In the CGSM, shear modulus and damping ratio of the soil are functions of depth and shear strain, wave equation for the transmission of shear wave is obtained.
E denotes Young's modulus of the segmental ring, I is theareamomentofinertiaofthetunnelcross-section, G is the shear modulus, A is the tunnel cross-sectional area.
This solution performs well in evaluating the coefficient of subgrade modulus (k) at any buried depth, particularly for relatively shallowly buried shield tunnels.
The only differences are that the original length, area, and change in length represent different parts of the object, and that we use a different modulus.
This indicates that the Vesic foundation reaction modulus expression indeed underestimates the relative stiffness of the tunnel soil and thus overestimates the tunnel settlement.
This means taking one number, the base, to the power of another number, the exponent, and taking the remainder when dividing by a third number, the modulus.